Hydraulic pumps and motors of the radial piston type may comprise a rotor which is rotatably mounted on a stationary pintle valve. A typical pump of this type is disclosed in U.S. Patent Application Ser. No. 425,192, filed on Dec. 17, 1973 by William Carl Engel for "High Pressure Radial Piston Fluid Translating Device and Cylinder Construction Therefore", now U.S. Pat. No. 3,878,767. Such application, assigned to the assignee of this application, is adapted to operate at a maximum speed approximating 12,000 rpm with internal fluid pressures reaching levels as high as 7,500 psi.
A conventional sleeve bearing is normally disposed in a bore formed in the rotor to rotatably mount the rotor on a pintle valve. Many such bearings exhibit a relatively short life expectancy due to their separation from the rotor as a result of continued use at high speeds and subjection thereof to high operating pressures in the range mentioned above. Methods and apparatus for forming bearings of this type are disclosed in U.S. Pat. Nos. 3,280,758; 3,707,035; and 3,709.108.